Elastic band heat activation system

ABSTRACT

An elastic band activation apparatus for activating a heat-sensitive thermal film attached to an edge of a body of an article to form an elastic band along the edge of the article. The apparatus has at least one chamber with a heating zone having a shrinkage atmosphere at a first temperature sufficiently elevated to activate the heat-sensitive thermal film to shrink the film to form the elastic band. The chamber may also have a cooling zone with a quench atmosphere at a second temperature which is less than the first temperature to arrest the shrinkage of the heat-sensitive thermal film. An article transporter transports the article through the heating zone and then through the cooling zone. The apparatus may also include two lateral compression bars for spreading apart first and second adjacent edges of an article when transported through the chamber to expose the article interior region to activate first and second heat-sensitive thermal films, thereby forming first and second elastic bands. Alternate methods of forming elastic bands along an edge of an article are also provided.

BACKGROUND OF THE INVENTION

The present invention relates generally to an elastic band heatactivation system, including a method and apparatus for activating aheat-sensitive thermal film attached to an edge of a body of an articleto form an elastic band along the edge of the article.

For example, the article may be an elasticized disposable headband orsweatband, a hospital surgical gown, a surgical hat, a pair of surgicalbooties, or a disposable incontinence garment, such as a disposablediaper with the elastic band formed thereon being a waistband. For thepurposes of illustration, the finished product discussed herein will bea disposable diaper with an elastic waistband. It should be clear thatthe objects, techniques, features and advantages of the presentinvention may be applied to any such article to form an elastic bandalong the edge of the article.

Other activation systems have been used to activate a heat-shrinkablefilm located in a waistband portion of a disposable diaper to promote ahigh production rate without excessively heating the remaining portionsof the diaper. These earlier systems included a continuous productionapparatus having an enclosed heating zone in which hot air is blowntoward the waistband portion of a plurality of disposable diapers, eachhaving an elastic heat-shrinkable film attached thereto. The diapers aretransported through the enclosed heating zone on an endless conveyor. Toincrease the energy efficiency of the system, the hot air is recycled.After heating the waistband, the diapers are allowed to cool to ambienttemperature using the natural convection currents within a room wherethe diapers are located.

One known apparatus has an inverted U-shaped heating shroud throughwhich the diapers are conveyed. The shroud has a plurality of jetopenings for directing hot air jets toward the waistband portions of thediaper. The shroud may be automatically raised and lowered relative tothe path of travel of the diapers to regulate the heat applied thereto.A greater volume of air is drawn off the diapers than the volume of hotair supplied to the waistband portions, so cooler ambient air is drawnover the remaining portions of the diapers and the components of theapparatus and extracted with the hot air.

In these known systems, the disposable diaper is folded along atransverse axis, so that the front waistband portion lies adjacent tothe back waistband portion. The diapers are then transported in thisstate with the front and back waistband portions adjacent one anotherand directed toward the hot air source. Disadvantageously, the closeproximity of the front and back waistband portions often prevents thehot air from entering the region of the diaper between the front andback waistband portions. This often results in non-uniform heating ofthe heat-shrinkable film which may cause improper shrinkage of theelastic, resulting in an inconsistent product.

After heating in these known systems, the gradual cooling to ambienttemperature does not provide a controlled duration of heating. Thisuncontrolled heating duration may disadvantageously produceinconsistencies in the final finished products. Therefore, the earlierknown systems often produce inconsistent products on a given assemblyline, increasing the quality control problems for the articlemanufacturer, which in turn drives up the product cost.

Thus, a need exists for an improved elastic band heat activation system,including a method and apparatus, for activating a heat-sensitivethermal film attached to an edge of a body of an article to form anelastic band along the edge of the article, which is not susceptible tothe above limitations and disadvantages.

SUMMARY OF THE INVENTION

It is an overall object of the present invention to provide an improvedelastic band heat activation system for activating a heat-sensitivethermal film attached to an edge of a body of an article to form anelastic band along the edge of the article.

A further object of the present invention is to provide an improvedelastic band heat activation apparatus for consistently producing aplurality of high quality articles having an elastic band along an edgeof the article.

An additional object of the present invention is to provide an improvedelastic band heat activation system which is energy efficient and costeffective to operate.

Another object of the present invention is to provide an improved methodof activating a heat-sensitive thermal film attached to a first edge ofa body of an article.

Still another object of the present invention is to provide an improvedmethod of activating a heat-sensitive film which produces a plurality ofarticles having a consistently high quality elastic band along an edgeof each article.

Yet another object of the present invention is to provide an improvedmethod of activating a heat-sensitive film attached to an edge of a bodyof an article, the method being capable of implementation with currentproduction methods of assembling of such articles.

According to one aspect of the present invention, an elastic band heatactivation apparatus is provided for activating a heat-sensitive filmattached to a first edge of a body of an article to form an elastic bandalong the first edge of the article. The apparatus includes at least onechamber having a heating zone with an atmosphere at a first temperaturesufficiently elevated to activate the heat-sensitive thermal film toshrink the film to form an elastic band. The chamber also has a coolingzone with an atmosphere at a second temperature which is less than thefirst temperature. The apparatus includes an article transporter fortransporting the article first through the heating zone to activate theheat-sensitive thermal film, and then through the cooling film to arrestthe shrinkage of the heat-sensitive thermal film. In this manner, theelastic band is formed.

According to another aspect of the present invention, an elastic bandheat activation apparatus for activating a thermal film as describedabove includes at least one chamber. The chamber has a heating zone withan atmosphere at a first temperature sufficiently elevated to activatethe heat-sensitive thermal film to shrink the film to form an elasticband. The apparatus includes an article transporter for transporting thearticle through the heating zone to activate the film. The apparatusalso has lateral compression means within the chamber for laterallycompressing the body in a direction generally parallel to a first edgeof the article along which the thermal film is attached. The body islaterally compressed while the article is transported by the articletransporter through the heating zone, to aid in the formation of theelastic band.

According to a further aspect of the present invention, an elastic bandheat activation apparatus for activating a thermal film as describedabove includes at least one chamber having a heating zone and a coolingzone as described above. The apparatus also includes an articletransporter and lateral compression means, both as described above.

In an illustrated embodiment, the chamber comprises a common housing forat least partially enclosing both the heating and cooling zones. Thechamber also has hot gas exhaust means for exhausting the heated gas asan exhaust gas after it has activated the thermal film. The apparatusalso has hot gas recycling means coupled to the hot gas exhaust meansfor receiving the exhaust gas, reheating it and returning at least aportion of the reheated exhaust gas to the heating zone. Additionally,the heating zone may be divided into a preheating zone and a mainheating zone. The preheating zone may receive the exhaust gas from themain heating zone, with or without being reheated. Monitoring means andcontrol means responsive to the monitoring means are also provided formonitoring and controlling the apparatus.

According to yet another aspect of the present invention, a method isprovided of activating a heat-sensitive thermal film attached to a firstedge of a body of an article to form an elastic band along the firstedge of the article. The method includes the steps of heating the firstedge of the article to a first temperature sufficiently elevated toactivate the heat-sensitive thermal film to shrink the film to form theelastic band. In a cooling step after the heating step, the first edgeof the article is cooled to a second temperature which is less than thefirst temperature to arrest the shrinkage of the heat-sensitive film.

According to yet another aspect of the present invention, a method isprovided of activating a heat-sensitive film as described above. Themethod includes the steps of heating the first edge of the article to afirst temperature sufficiently elevated to activate the heat-sensitivethermal film to shrink the film to form the first elastic band. In acompressing step, the article is laterally compressed during the heatingstep to aid in formation of the first elastic band.

These and other objects, features and advantages of the presentinvention will become apparent to those skilled in the art from thefollowing description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of one form of an elastic band heatactivation apparatus of the present invention shown working inconjunction with a diaper stacking machine or diaper stacker whichserves as an article transporter in this form of the present invention;

FIG. 2 is a partial, enlarged perspective view of the articletransporter of FIG. 1;

FIG. 3 is an enlarged partially cutaway perspective view of one form ofa chamber of an elastic band heat activation apparatus of the presentinvention;

FIG. 4 is a top plan view of the chamber of FIG. 3;

FIG. 5 is a vertical sectional view taken along line 5--5 of FIG. 4;

FIG. 6 is a vertical sectional view taken along lines 6--6 of FIG. 4;and

FIG. 7 is a partially schematic diagram of one form of a gas handlingsystem and a control system of the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 illustrates an embodiment of an elastic band heat activationapparatus 10 constructed in accordance with the present invention forforming an elastic band along an edge of an article. By way ofillustration, the activation apparatus described is used to form anelasticized waistband W (FIG. 2) of a disposable diaper D having a bodyB. In FIG. 2, the diaper D is shown in a folded condition with edge E₁adjacent edge E₂, defining an interior region R therebetween. Thewaistband portion W comprises front and back waistband portions W₁ andW₂ along respective edges E₁ and E₂.

Such disposable diapers typically have a moisture impervious outer sheetor layer L_(o), and a moisture pervious non-woven body-contacting innersheet or layer L_(i). A moisture absorbent filler pad core or layerL_(f) is sandwiched and encased between the inner and outer layers L_(i)and L_(o). The encasement of the diaper may be accomplished by bondingthe layers together by plurality of fine hot melt adhesive lines (notshown).

The manufacture of disposable diapers is well known in the art. Oncesuch diaper and method of manufacture is illustrated in U.S. Pat. No.4,726,807 to Richard H. Young and Peter Lancaster, which is hereinincorporated by reference to illustrate the typical materials used andmethods of manufacturing such diapers.

For example, the moisture impervious outer layer L_(o) may be of a thinthermal plastic material, such as a pigmented polyethylene film having athickness in the range of 0.02-0.04 mm. The moisture pervious innerlayer L_(i) may typically be of a carded polyester fiber with a latexbinder or of a spun-bonded polypropylene having continuous fibers andthermally bonded by patterned calendar rolls. The moisture absorbentlayer L_(f) may be of any suitable material with fibrous materialscommonly being used. For example, wood fibers or other fibers, such aschemical wood pulp, or any other suitable liquid absorbing material,such as commercially available fluff pulp, or of a fluffed bleachedkraft softwood pulp may be used with or without other fibers and liquidabsorbing chemicals. The hot melt adhesive lines (not shown) may be ofthe flexible rapid setting variety, such as those formulated fromethylene-vinyl acetate resins used with tackifiers and other additives.

To assemble the waistband portions W₁ and W₂, fine lines of adhesive A(FIG. 2), which may be of the hot melt variety described above, areapplied to the inner side of one or both of the inner and outer layersL_(i) and L_(o) along the waistband edges E₁ and E₁. Although not shownin FIG. 2, waistband W₁ is constructed in the same manner as illustratedfor waistband W₂. Strips F₁ and F₂ of a heat-sensitive thermal film Fare sandwiched between the inner and outer layers L_(i) and L_(o) alongthe respective waistband edges E₁ and E₂ using the fine lines ofadhesive A. Upon exposure to heat, the film F contracts to form anelastic band along the edge of the article, here along the waistbandportion W of diaper D.

One suitable heat-sensitive thermal film F is known as Fulflex BlendIII, which may be obtained from the Fulflex Company, P.O. Box 4549,Middletown, R.I. 02840. Suitable dimensions for the film strip may be anominal thickness of 1 mil (0.001 inches) 50 mm long and 12.7 mm wide.For elasticized diaper waistbands, the ability of the elastic waistbandto return to the original contracted form after being stretched to amaximum elongation may be a 5-9% memory loss (with a nominal value of7%). An ideal tension value, that is the amount of force needed todeflect the waistband to eighty percent of the difference between theminimum and maximum stretch, may be on the order of 260 to 300 grams(with a nominal value of 280 grams). The percent elasticity (orshrinkage), that is, the increase in width of the waistband from arelaxed position to the waistband ultimate width, may be on the order of20-30%. These characteristics are of course variable.

The activation apparatus 10 includes a housing or shroud 12 having anentrance end 14 and an exit end 16. A diaper stacking machine or diaperstacker S serves as an article transporter 18 for transporting thediapers in a direction indicated by arrow X through shroud 12 from theentrance end 14 to the exit end 16. The shroud 12 may be permanentlyattached to the stacker S or the shroud may be raised and lowered fromthe stacker in a direction indicated by arrow Y using hydraulic,pneumatic, or other actuating means (not shown).

Referring to FIG. 3, the illustrated shroud 12 defines at least onechamber, such as a heating chamber 20 for at least partially enclosing amain heating stage or zone 22. To enhance the efficiency of theactivation apparatus 10, the shroud 12 may also define a preheat chamber24 for at least partially enclosing a preheating stage or zone 26. Thepreheating zone 26 is located adjacent the shroud entrance 14. Theactivation apparatus 10 may also include a cooling or quench chamber 30,such as that defined by shroud 12. The cooling chamber 30 is locatedadjacent the shroud exit end 16, and defines therein a quench or coolingstage or zone 32.

Referring also to FIGS. 4-6, the main heating chamber 20, the preheatchamber 24 and the cooling chamber 30 are defined by two interiorupright sidewalls 34 and 36 and an interior upper wall 38. The mainheating and preheat chambers 20 and 24 may be partially separated by anupright wall 40. Similarly, the heating and cooling chambers 20 and 30may be partially separated by upright wall 42. Thus, the illustratedshroud 12 serves as a common housing for at least partially enclosingthe preheat, main heating and cooling zones.

Before describing in detail the construction of the shroud 12, the gashandling system 48 of the activation apparatus 10 will be described withreference to FIG. 7. The activation apparatus 10 has a main heatingchamber hot gas source 50 including a main heating supply blower 52which blows a hot gas, such as air, across the heating coils of a mainheater 54. The heated gas moves through a duct 58 from the main heater54 through a volume damper 56 in duct 58. The duct 58 is coupled to aninlet 60 of the main heating chamber 20. The moving hot gas iscirculated through the main heating zone 22 in a manner describedfurther below, to produce an exhaust gas which exits the shroud 12through a main heating chamber outlet 62.

The preheating stage 26 has a preheat chamber inlet 64. In analternative embodiment, the heated exhaust gas may be delivered directlyfrom the main heating chamber outlet 62 to the preheat chamber inlet 64via ductwork (not shown). In this case, the hot gas source blower 52receives makeup inlet air directly from the atmosphere.

A heat recycling system is illustrated including recycling means 70coupled to the main heating chamber outlet 62 via a duct 72. Therecycling means has a hot exhaust gas blower 74 that draws the exhaustedhot gas from chamber 20. To control the volume of gas removed from themain heating chamber 20, the recycling means 70 has a volume damper 76in duct 78 exiting the exhaust blower 74. The activation apparatus 10may also include a heat recovery system 80 including an air-to-airrotary heat exchanger 82. The heat exchanger 82 receives the exhaustedhot gas from duct 78 and vents this gas to atmosphere through duct 84.The rotary heat exchanger 82 receives makeup inlet air through duct 86and heats the makeup air using heat from the exhausted hot gas. Theheated makeup inlet air then exits the heat recovery system 80 via duct88.

Alternatively, at least a portion of the exhausted hot gas may bebypassed around the heat recovery system 80 via bypass duct 90 whichinterconnects ducts 78 and 88. The bypass duct 90 has a volume damper 92to control the amount of exhausted hot gas bypassed around the heatrecovery system 80.

The illustrated activation apparatus 10 has a preheat gas source 100.The preheat gas source 100 includes a preheat blower 102 which receivesthe heated inlet makeup gas or the bypassed hot exhaust gas from duct88. A volume damper 104 regulates the gas flow from the preheat blower102 to the coils of a preheat heater 106, thereby producing a preheatedmoving gas. The preheated moving gas is delivered from the preheat gassource 100 to the preheat chamber inlet 64 via duct 108. After thepreheat gas is circulated through the preheating zone 106, as describedfurther below, it is exhausted through a preheat outlet 110. Theexhausted preheat gas is drawn by the main blower 52 from the preheatoutlet 110 to the main heating chamber hot gas source 50 via duct 112.

One form of overall recycling system of the illustrated activationapparatus 10 includes heater means comprising heaters 106 and 54 forreheating the recycled exhaust gas. The recycling system has means,including bypass duct 90 and volume damper 92, for returning at least aportion of the reheated exhaust gas to the heating zone. In thealternative embodiment of FIG. 1 which lacks a preheating stage,ductwork (not shown) couples duct 78 from the recycling means 70 to amain heating chamber hot gas source inlet duct.

In the the alternative embodiment mentioned above, wherein the mainheating chamber exhaust gas is delivered to the preheat chamber inlet64, the apparatus 10 may include a heat recovery system, such as system80. This heat recovery system would receive the preheat chamber exhaustgas from outlet 110 before venting to atmosphere. An air-to-air rotaryheat exchanger, such as exchanger 82, would then heat makeup airreceived from the atmosphere using heat from the preheat chamber exhaustgas. The hot gas source 50 would then receive the heated makeup air fromthe rotary heat exchanger.

The activation apparatus 10 also has a cool gas source 120 of movingquench or cooling gas, such as air. A cooling gas supply blower 122receives makeup or supply air from the atmosphere via duct 124. Themakeup air from the cooling supply blower 122 is then cooled, such as byforcing the makeup air across cooling coils of a cooling orrefrigeration unit 126. The volume flow of the gas through therefrigeration unit 126 is regulated by volume damper 128 as it exits therefrigeration unit via duct 130. Duct 130 couples the cool gas source120 a cooling chamber inlet 132 to deliver the moving cooling gas to thecooling zone 32.

After the cooling gas has circulated through the cooling zone 132 asdescribed further below, it is exhausted through a cooling chamberoutlet 134. The exhausted cooling gas is delivered from outlet 134 backto the cool gas source 120 via duct 136. A volume damper 138 regulatesthe volume of cooling gas drawn from the cooling zone 32 by a coolingexhaust blower 140. The exhausted cooling gas is then vented toatmosphere from cooling blower 140 via duct 142.

To prevent overheating within the main heating chamber 20, a bypass duct144 may be included between the cool gas inlet duct 130 and the hot gassource outlet duct 58. The duct 144 has a volume damper 146 to controlflow through the duct.

Now that a suitable overall gas handling system 48 is understood, theconstruction and operation of the illustrated shroud 12 will bedescribed with reference to FIGS. 4-6. In the illustrated embodimentincluding the preheating stage 26, the preheated gas is delivered to thepreheat chamber inlet 64. The preheat inlet 64 penetrates through anouter upper wall 150 and an intermediate upper wall 152 of the shroud 12to deliver the preheated gas into a preheat inlet plenum 154. Thepreheat inlet plenum 154 is bounded at its top and bottom by therespective walls 152, 38, at one end by a section of the wall atentrance end 14, at its other end by an upright wall 40a and at itssides by upper sections of the interior shroud walls 34, 36.

Gas from the preheat inlet plenum 154 is typically directed to thepreheat chamber 26 by a gas directing surface having a plurality ofnozzles, such as nozzles 156 extending through the inner upper wall 38.The nozzles 156 direct jets of preheat gas at the upper edges E₁ and E₂(FIG. 3) of each diaper D being moved through the preheating zone 26 bythe transport means 18.

While the nozzles 156 in FIGS. 4-6 are schematically illustrated ascircular in nature, slot nozzles may also be used. For example, the slotnozzles may each be three inches long, with a 0.0625 inch nozzle gap.For an eighteen inch long heating chamber 20, such as for the shroudembodiment shown in FIG. 1 without a preheat chamber, the nozzles may bespaced one inch apart along the length of the heating chamber 20.Baffles and other air direction devices may be used in addition to or inlieu of nozzles.

The preheat gas is exhausted from the preheating zone 26 through aplurality of outlet apertures 158 (FIG. 5) through the interior uprightsidewalls 34 and 36 and to a preheat outlet plenum 160. The preheatoutlet plenum 160 is defined by the interior upright sidewalls 34 and36, outer sidewalls 162 and 164 of shroud 12, a contact surface 165(FIG. 7) of stacker S, the shroud upright wall at entrance end 14, anupright wall 40b (FIG. 5) which may be coplanar with wall 40, and therespective outer and intermediate upper walls 150 and 152. Thus, thepreheat inlet and outlet plenums are configured in a compact, stackedrelationship, one above the other. The exhausted preheat gas isexhausted from the preheat outlet plenum 160 via the preheating chamberoutlet 110.

The main heating stage inlet 60 extends through the outer andintermediate upper walls 150 and 152 to deliver the moving heated gas toa main heat inlet plenum 166. The main heat inlet plenum 166 is definedby the inner and intermediate upper walls 38 and 152, sections of walls34, 36, wall 40a, and an upright wall 42a which may be coplanar withwall 42. An outlet of the main heat inlet plenum serves as inlet meansfor the main heating zone 22 and may comprise a gas directing surface,such as a surface with a plurality of nozzles 168 extending through theinner upper wall 38. The nozzles 168 direct jets of hot gas toward theedges E₁ and E₂ of each diaper D (FIG. 3) being moved through theheating zone 22 by the transport means 18.

The main heating chamber has hot gas exhaust means including a mainheating zone outlet plenum 170. The outlet plenum receives the hotexhaust gas from the main heating zone 22 through a plurality ofapertures 172 extending through the inner upright sidewalls 34 and 36.The hot gas outlet plenum 170 is defined by the sidewalls 34 and 36, theextended upright shroud sidewalls 162 and 164, the stacker contactsurface 165 (FIG. 7), the upright walls 40b and 42b, and the outer andintermediate upper walls 150 and 152. The hot exhaust gas is drawn bythe exhaust blower 74 from the hot gas outlet plenum 170 through themain heating outlet 62. The illustrated shroud thus also has stackedupper and lower heat plenums 166, 170.

The cooling chamber inlet 132 extends through the outer and intermediateupper walls 150 and 152 to deliver the moving cooling gas to a coolinginlet plenum 174. The cooling inlet plenum 174 is defined by theintermediate upper wall 152, the inner upper wall 38, portions of walls34, 36, the upright wall 42a, and an upright wall defining the exit end16 of shroud 12. A gas directing surface such as wall 38 with aplurality of nozzles directs the cool gas flow to the upper edges E₁ andE₂ of each diaper D being moved through the cooling zone 32 by thetransport means 18.

After circulating through cooling zone 32, the cooling gas is exhaustedthrough a plurality of apertures, such as 178, extending through theupright inner sidewalls 34 and 36. The cooling zone includes coolingzone exhaust means comprising a cooling outlet plenum 180 receiving theexhausted cooling gas through apertures 178. The cooling outlet plenum180 is defined by the inner upright sidewalls 34 and 36, the outersidewalls 162 and 164, the stacker contact surface 165 (FIG. 7), theupright wall 42b, the upright wall defining the shroud exit end 16, andthe outer and intermediate upper walls 150 and 152. The exhaustedcooling gas is drawn from the cooling outlet plenum 180 by the coolingexhaust blower 140 through the cooling chamber outlet 134. The plenums174, 180 are also thus stacked to provide a compact design.

The main heating zone and cooling zone inlet nozzles 168 and 176,illustrated as circular in nature, may also be slot nozzles, asdescribed above for the preheat zone inlet nozzles 156 or other airdirecting devices. The slot nozzles 168 and 176 may, for example, bespaced one inch apart along the path of travel of the diapers D throughthe shroud 12.

The desired operating values within shroud 12 of temperature, gas flowvelocity and gas flow volume are furnished as a desired value inputsignal 188 to a controller 190, shown in FIG. 7. The temperature, gasflow velocity and volume requirements within shroud 12 depend upon thetype of thermal film F used and the type of article upon which theelastic band is formed. Thus, the main heating zone 22 has a shrinkageatmosphere with a shrinkage temperature which is sufficiently elevatedto activate the heat-sensitive thermal film F to shrink the film to forman elastic band on a given article.

In the disposable diaper example, using Fulflex Blend III as the film F,an acceptable elastic waistband W is formed with a desired shrinkage (orpercent elasticity) in excess of twenty-five percent, and with anelastic tension of approximately 280 grams. This acceptable waistband Wmay be formed by applying hot air at 230° F. for four seconds at avelocity of 1,200 feet per minute (fpm). The time duration during whichthe heated gas is applied to the waistband portions depends upon thespeed with which the transport means 18 moves the diapers D throughshroud 12 and the physical length of the heating chamber. For example,the two stage shroud 12 shown in FIG. 1 (having no preheating stage) maybe approximately twenty-four inches long, with an eighteen inch longmain heating chamber 20 and a six inch long cooling chamber 30. Thisembodiment requires an air flow of approximately 70 cubic feet perminute (cfm). However, it is believed that suitable elastic filmactivation may be obtained at temperatures between about 160° F. andabout 250° F. Furthermore, suitable results may be obtained attemperatures between 160° F. and 230° F. with increased air velocity,such as on the order of 1,650 fpm.

To control the shrinkage of the elastic film, and arrest or stop theactivation process, the diapers D are quenched by transporting them fromthe heating zone 22 through the cooling zone 32. The cooling zone alsoadvantageously cools the entire diaper, in addition to the waistbandarea, to minimize and prevent any damage to the balance of the diaperfrom the elevated temperatures encountered in the heating zone 22.

The quench atmosphere within the cooling zone is at a quench temperatureless than that within the heating zone 22. For example, the temperaturewithin the cooling zone 32 may range between about 35° F. and about 100°F. The preheat atmosphere within the preheating stage 26 may be at anintermediate preheat temperature between the shrinkage temperature inthe heating zone 22 and the quench temperature in the cooling zone 32.

The air flow velocities and volumes within the preheat chamber 24 andcooling chamber 30 may be the same as, or different than the valueswithin the heating zone 22. However, in the preferred embodiment, theshroud is neutrally or overpressurized so equal or greater volumes ofair are supplied to each chamber 20, 24 and 30 than are removed via theoutlets from each respective chamber.

The desired operating conditions, such as those outlined above forforming disposable diaper elasticized waistbands, are set by an operatoror by automated means (not shown) to provide the desired value inputsignal 188 to controller 190. To control and maintain the desiredoperating conditions, the controller 190 receives a series of inputsignals from various sensors and monitors. For example, the temperaturewithin each of the preheating, main heating, and cooling zones 26, 22and 32, are monitored by temperature monitor means, such as internalthermocouples (not shown) within each stage. The thermocouples withinthe preheating, main heating, and cooling zones 26, 22 and 32, maysupply output readings to temperature gauges 192, 194 and 196,respectively. The controller 190 receives preheat, main heating, andcooling temperature signals 198, 200 and 202 from the preheat, mainheating and cooling zone thermocouples, respectively.

A speed monitor or sensor 204 is positioned to monitor the speed of thetransport means 18 carrying the diapers D through shroud 12. The speedsensor 204 may be an optical or mechanical transducer which provides aspeed input signal 206 to controller 190.

To monitor the velocity of the gas flow within the preheat, mainheating, and cooling chambers 24, 20 and 30, gas velocity monitoringmeans, such as vane anemometers (not shown) may be positioned atappropriate locations within shroud 12, or at other locations within thegas handling system 48. The vane anemometers generate flow input signals(not shown) corresponding to the measured gas flows. The flow inputsignals are received and processed by controller 190, and along withdesired values signal 188, the speed sensor signal 206 and thetemperature signals 198, 200 and 202 to regulate the activationapparatus 10. The controller 190 may be a computerized analog or digitalcontrol system, such as a microprocessor, or a portion of the controlsystem for the overall diaper assembly line.

The temperature and flow of the moving heated gas through the mainheating zone 22 are controlled by heating zone temperature and flowcontrol means comprising the controller 190 generating a plurality ofshrinkage control signals coordinated to provide the desired shrinkageatmosphere. The controller 190 controls the inputs to the main heatingzone 22 by providing a main heater control signal 208 to the main heater54, and a damper control signal 210 to the volume damper 56. Controller190 provides a damper control signal 212 to volume damper 76 to controlthe volume of exhaust gas drawn from the main heating zone 22 by theexhaust blower 74.

During normal operation, volume damper 146 is closed, preventing coolinggas from flowing through bypass duct 144. In an overheat emergency, thethermocouples within the main heating zone 22 detect a dangerously hightemperature and provide a corresponding high temperature input signal200 to controller 190. In response, the controller 190 sends an overheatemergency damper signal 214 to the overheat emergency bypass volumedamper 146. The emergency signal 214 fully opens the damper 146 to dumpcooling gas to the main heating zone input 60 which cools down theheating zone 22.

The temperature and flow of preheat gas moving through the preheatingstage 26 are controlled by preheat zone temperature and flow controlmeans comprising the controller 190 generating a plurality of preheatcontrol signals coordinated to provide a desired preheat atmosphere. Thepreheat atmosphere is determined by the settings of the preheat heater106, input volume dampers 92 and 104, and output volume damper 56 whichcontrols the volume of gas drawn from the preheat chamber by blower 52.The controller 190 controls the inputs to the preheat zone 26 byproviding damper control signals 220 and 222 to dampers 92 and 104,respectively. The controller 190 controls the preheat heater 106 with apreheat temperature control signal 224.

The temperature and flow of cooling gas through the cooling zone 32 arecontrolled by cooling zone temperature and flow control means comprisingthe controller 190 generating a plurality of quench control signalscoordinated to provide a desired quench atmosphere. The quenchatmosphere is determined by the settings of refrigeration unit 126,volume dampers 128 and 138, and during an overheat emergency, by theoverheat emergency bypass volume damper 146. The controller 190 controlsthe refrigeration unit 126 with a cooling zone temperature controlsignal 226. The controller provides volume dampers 128 and 138 withdamper control signals 228 and 230, respectively.

The activation apparatus 10 may also include variable lateral compactor,such as a side edge compactor 240, for spreading apart the edges E₁ andE₂ to expose the interior region R of the diaper D being transported bythe article transporter 18 through shroud 12. The illustrated compactor240 has two opposing horizontal compression bars 242 and 244. Thecompression bars 242 and 244 are each mounted to an L-shaped mountingmember. For example, the compression bar 244 is mounted to vertical leg246 which joins horizontal leg 248 of the L-shaped mounting member. Thecontact surface 165 of stacker S has a recess 249 to slidably receivehorizontal leg 248 for motion in a direction indicated by arrow Z inFIG. 3. The recess 249 is sized so the horizontal mounting portion 248of the compactor is flush with the stacker surface 165 to provide a sealalong a portion of the bottom edge along the shroud 12.

Referring to FIGS. 2 and 3, the transport means 18 includes an endlessbelt 250 having a plurality of separator plates, such as 252a, 252b,252c and 252d projecting outwardly therefrom. The diapers D may bereceived between each of two adjoining plates, such as 252a and 252b,from a diaper assembly line (not shown). Each separator plate 252includes two opposing, compression bar receiving, recesses or slots 254and 256. Upon entering the shroud 12, the compression bar 242 isreceived by slots 254 of each separator plate, and compression bar 244is received by slots 256.

At the shroud entrance end 14, the compression bars 242 and 244 have agradual outward curve, such as curve 258 on bar 244. The curve 258allows the compression bars to gradually engage the sides of diaper D asit enters the shroud, and to gradually compress the diaper D in alateral direction generally parallel to the waistband edges E₁ and E₂.This lateral compression forces apart edges E₁ and E₁ to expose theinner region R and the inner layer L₁ of the diaper to the preheat andmain heating gases.

It is apparent that other side edge compactors 240 may also be used,such as one having a fixed side (in lieu of compression bar 242) againstwhich the diaper D is compressed by a variable compression member (notshown). Other side edge compactors may be used to gather the diaper bodyB along the edges E₁ and E₂, with such compactors positioned to direct acompacting force against the side edges of the diaper. For example, airjets (not shown) may be used to provide the compactor compacting force.

The variable compactor 240 may be controlled by compression controlmeans, such as a hydraulic or pneumatic compression actuator (notshown), for moving the compression bars 242 and 244 as indicated byarrow Z. For example, the controller 190 provides a compression controlsignal 260 to the drive compactor actuator (not shown). Thus, a desireddegree of compression may be imparted to the edges E₁ and E₂.

In this manner, the separation of the first second edges E₁ and E₂allows the moving heated gas to enter the interior region R of thediaper. The moving heated gas activates the first and secondheat-sensitive thermal films F₁ and F₂ to shrink and form the first andsecond elastic waistbands W₁ and W₂, respectively. The exposure of thenon-woven inner layer L_(i) to the heated gas is believed to provide forquicker activation of the thermal film F. Furthermore, the compressionof the diapers D by the compactor 240 minimizes the tendency of thefiller layer L_(f) to retard contraction of the thermal film F. Thus,the pregathering or bunching of the body of the diaper at the edges E₁and E₂ by compactor 240 promotes more rapid activation of film.

In operation, the activation apparatus 10 is mounted to a stacker Swhich serves as transporter means for transporting the diapers D throughshroud 12. The shroud 12 may be either permanently attached to stackerS, or may be raisable therefrom in a direction indicated by arrow Y byraising actuator means (not shown). The raising actuator means may beresponsive to a shroud raising and lowering control signal (not shown)from controller 190.

For example, during start-up, it may be advantageous to have the shroud12 raised above the stacker contact surface 165 while the preheat, mainheat and cooling gases are brought to temperature. Once the desiredtemperature and air flow are reached, the shroud 12 is lowered intoposition adjacent the stacker contact surface 165. During emergencyconditions, such as over-temperature, fire and the like, the shroud 12may be raised above stacker S to minimize damage to the diapers D movingtherethrough.

In discussing the operation of the activation apparatus 10, a firstmethod is also illustrated of activating a heat-sensitive thermal film Fattached to a first edge of a body of an article, such as diaper D toform an elastic waistband W. In a two stage shroud, such as illustratedin FIG. 1, in a heating step conducted within the heating chamber 20,the edges E₁ and E₁ of the article are heated to a first temperature.Thermocouples within the heating zone monitor the temperature thereinand provide a temperature signal to temperature gauge 194 and the signal200 to controller 190. In response to the temperature input signal 200and the desired value signal 188, the controller generates the mainheater signal 208 to drive the main heater 54. The desired firsttemperature is chosen to be sufficiently elevated to activate theparticular type of heat-sensitive thermal film F in a given article toform the elastic band, such as waistband W₁ and W₂.

In a cooling step, edges E₁ and E₂ are actively or force cooled afterthe heating step to a second temperature which is less than the firsttemperature to arrest the shrinkage of the heat-sensitive film F. Thecooling step may include the step of directing the cooling gas at thesecond temperature toward edges E₁ and E₂ of the diaper. Thermocoupleswithin the cooling zone 32 monitor the temperature therein which may beread on temperature gauge 196. The cooling zone thermocouples provide acooling zone temperature signal 202 to controller 190. Controller 190controls the temperature within the cooling zone by providing coolingdamper control signals 228 and 230 to control volume dampers 128 and138, respectively. The controller 190 also controls the temperaturewithin the cooling zone by driving the refrigeration unit 126 with therefrigeration control signal 226.

To activate many suitable thermal films F, it is believed that theheating step comprises the step of supplying a heated gas at a firsttemperature between about 160° F. and about 250° F. to the heating zone22. Heated gas jets are directed toward edges E₁ and E₂ by nozzles 168.The cooling step further includes the step of supplying a cooling gas ata second temperature to the cooling zone 32. For many suitable films F,the second temperature is between about 35° F. and about 100° F.

For a three stage shroud, such as shown in FIGS. 3-7, the method alsoincludes the steps of preheating edges E₁ and E₂ to a third intermediatetemperature which is between the first and second temperatures.Thermocouples monitor the temperature within the preheating stage 26which may be read at temperature gauge 192. The thermocouples provide apreheat stage temperature signal 198 to controller 190. To maintain thepreheating zone temperature at a desired value, controller 190 providesa preheating heater control signal 224 to the preheat heater 106. Thecontroller 190 also provides volume damper control signals 220, 222, and210 to volume dampers 92, 104 and 56, respectively.

In a recycling step, the exhaust gas from the main heating zone 22 isreceived by recycling means 70 to provide a preheating heat source, suchas by exiting through the rotary heat exchanger 82 to atmosphere, or bybeing an input to the preheat gas source 100, via bypass duct 90.

The method also includes the steps of conducting the heating and coolingsteps within at least one chamber, such as shroud 12, having a heatingzone 22 and a cooling zone 32 therein. The method also includes the stepof transporting the diaper D from the heating zone 22 through thecooling zone 32 using transporter 18.

The method may also include a step of laterally compressing the body Bof the diaper in a direction generally parallel to edges E₁ and E₂during the heating step to aid in formation of the elastic band. Thestep of compressing is accomplished by the horizontal compression bars242 and 244 laterally compressing the diapers after entering the shroudentrance end 14 or by any other suitable mechanism for applying a forceto the sides of a folded diaper. The degree of compression may beadjusted by the compactor controller signal 260. The control signal 260positions the compactor 240 at desired locations by moving the compactorin the direction indicated by arrow Z.

A second method of activating a heat-sensitive thermal film F attachedto edges, such as diaper edges E₁ and E₂, includes the steps of heatingthe edges E₁ and E₂ as described above. During the heating step, acompressing step of laterally compressing edges E₁ and E₂ of the articleis performed to aid in formation of the elastic waistbands W₁ and W₂.

The second method may also include the steps of laterally compressingthe diapers D to separate the first and second edges E₁ and E₁ to exposethe interior region R of diaper D. The heating step further includes thesteps of directing a moving heated gas at a temperature of at least thefirst temperature toward the first and second edges E₁ and E₂ of diaperD. In this manner, the moving heated gas is allowed to enter theinterior region R of the article to activate the first and secondheat-sensitive thermal films F. This method substantially simultaneouslyforms the first and second elastic waistbands W₁ and W₂.

Having illustrated and described the principles of my invention withrespect to a preferred embodiment, it should be apparent to thoseskilled in the art that my invention may be modified in arrangement anddetail without departing from such principles. For example, a variety ofother articles may be manufactured using these principles, which mayrequire modifications of the heating shroud, article transporter,separator plates 252, the compression bars 242 and 244, etc.Furthermore, suitable material substitutions and dimensional variationsfor the components of the activation apparatus may be made. I claim allsuch modifications falling within the scope and spirit of the followingclaims.

I claim:
 1. An elastic band heat activation apparatus for activating aheat-sensitive thermal film attached to a first edge of a body of anarticle to form an elastic band along the first edge of the article, theapparatus comprising:at least one chamber; the chamber having a heatingzone with an atmosphere at a first temperature sufficiently elevated toactivate the heat-sensitive thermal film to shrink the film to form anelastic band; a cool gas source of cooling gas at a temperature which isless than ambient temperature; the chamber having a cooling zone coupledto the cool gas source for receiving cooling gas to provide a coolingzone with an atmosphere at a second temperature which is less than thefirst temperature; and an article transporter for transporting thearticle first through the heating zone to activate the heat-sensitivethermal film and then through the cooing zone to arrest the shrinkage ofthe heat-resistance thermal film, thereby forming the elastic band. 2.An apparatus according to claim 1 further including:a hot gas source ofmoving heated gas at a temperature of at least the first temperaturecoupled to the heating zone; and the cool gas source comprising a sourceof moving cooling gas coupled to the cooling zone.
 3. An apparatusaccording to claim 2 wherein: the first temperature is between about160° F. and about 250° F.; andthe second temperature is between about35° F. and about 100° F.
 4. An apparatus according to claim 1 whereinthe chamber comprises a common housing for at least partially enclosingthe heating and cooling zones.
 5. An apparatus according to claim 1wherein:the chamber comprises a common housing for at least partiallyenclosing the heating zone and the cooling zone; the apparatus furtherincludes a hot gas source of heated gas; the heating zone includes hotgas inlet means coupled to the hot gas source for receiving anddirecting the heated gas toward the first edge of the article; and thecooling zone includes cool gas inlet means coupled to the cool gassource for receiving and directing the cooling gas toward the first edgeof the article so as to actively cool the film.
 6. An apparatusaccording to claim 5 wherein:the chamber includes hot gas exhaust meansfor exhausting the heated gas as an exhaust gas after the heated gas hasactivated the heatsensitive thermal film; and the apparatus furtherincludes a hot gas recycling system coupled to the hot gas exhaust meansfor receiving the exhaust gas, the recycling system including heatermeans for reheating the exhaust gas and means for returning at least aportion of the reheated exhaust gas to the heating zone.
 7. An apparatusaccording to claim 5 wherein:the first temperature is between about 160°F. and about 250° F.; and the second temperature is between about 35° F.and about 100° F.
 8. An apparatus according to claim 5 wherein:the hotgas inlet means comprises a first plenum having a first plenum outlet,with the first plenum receiving heated gas from the hot gas source, andthe first plenum outlet including a gas directing surface having aplurality of first apertures therethrough interconnecting the firstplenum with the heating zone; the cool gas inlet means comprises asecond plenum having a second plenum outlet, the second plenum receivingcooling gas from the cool gas source, and the second plenum outletincluding a gas directing surface having a plurality of second aperturestherethrough interconnecting the second plenum with the cooling zone;and the first and second apertures are positioned to direct therespective heated gas and cooling gas as gas jets only toward the firstedge of the article along which the heat-sensitive thermal film isattached while the article is transported by the transport means throughthe respective heating and cooling zones.
 9. An apparatus according toclaim 1 wherein the heating zone comprises a preheating stage and a mainheating stage, the main heating stage having an atmosphere at the firsttemperature, and the preheating stage having an atmosphere at a thirdintermediate temperature being between the first and secondtemperatures.
 10. An apparatus according to claim 2 furtherincluding:heating zone flow control means for controlling a rate of flowof the moving heated gas from the hot gas source through the heatingzone; cooling zone flow control means for controlling a rate of flow ofthe moving cooling gas from the cool gas source through the coolingzone; heating zone temperature monitor means for monitoring the firsttemperature; heating zone temperature control means for controlling thetemperature of the heated gas from the hot gas source in response to theheating zone temperature monitor means; cooling zone temperature monitormeans for monitoring the second temperature; and cooling zonetemperature control means for controlling the temperature of the coolinggas from the hot gas source in response to the cooling zone temperaturemonitor means.
 11. An apparatus according to claim 1 wherein:the articleincludes a first heat-sensitive thermal film attached to the first edgeto form a first elastic band along the first edge, the body of thearticle having a second edge opposing the first edge, and the articleincluding a second heat-sensitive thermal film attached to the secondedge to form a second elastic band along the second edge of the article,the article being transported by the article transporter in a foldedcondition with the first edge adjacent the second edge and definingtherebetween an article interior region; and the apparatus furtherincludes compression means for spreading apart the first and secondedges while the article is transported by the article transporterthrough the heating zone to expose the interior region of the article toactivate the first and second heat-sensitive thermal films to form thefirst and second elastic bands.